The invention is directed to a device for fine adjustment of a lathe turning tool bit of a rotating radial adjustment head with an adjustment member actuatable by a fluid, which acts upon a stiff spring member retaining the turning tool bit, which can be shifted elastically outwards, and with a rotary passage for the supply of the fluid, which is acted upon by the respective control pressure, to the adjustment member.
In a known radial adjustment head of this type, preferably used for machining the surface of a hollow cylinder and having a turning tool bit radially adjustable by hydraulic pressure with reference to the rotational axis of the drill head, the radial adjustment head, generally designated as drill head, is provided with a stiff parallel spring action joint for guiding of the turning tool bit. This parallel spring action joint is shifted radially outwards by small amounts by means of a piston or by an extension element. A pneumatic control pressure, generally an air pressure, is converted into a higher hydraulic working pressure by means of a pressure converter assigned to the drill head. The control pressure is fed as an adjustment pressure to the adjustment member, wherein oil under pressure can be replenished from an assigned storage container, if leakage losses arise within the hydraulic arrangement, compare DE-OS 24 26 409 (U.S. Pat. No. 3,977,194.
The piston of the pressure converter is pulled back with each start of a working process for compensation of leakage losses, so that a vacuum is formed in the region of the pressure oil. The vacuum opens a check valve so that the pressurized oil located in the storage container, which possibly is subjected to a slight overpressure, can flow back into the space provided for the liquid in the pressure converter. Since a revolving system must be balanced, the storage container and the check valve are arranged opposite each other in the known arrangement. In spite of this opposing arrangement of the storage container and check valve, out-of balance conditions resulting in vibrations are progressively generated by the storage leakage oil flowing into the hydraulic pressure system. Also, the oil stock must be small in order to avoid excessive inertia forces interfering with the rotational motion. In order to keep down this flawed behavior, the arrangement must be frequently shut down, in order to supplement the oil stock. In addition, the control air must be supplied through a rotary seal, which must be continuously lubricated, since otherwise at the high rpms the sealing lips would be rapidly destroyed. If the pressure converter and the radial adjustment head are to be designed as components separate from each other in space, then the pressurized oil must also be supplied to the radial adjustment head through a rotary transmission with a rotary seal. This is not easily possible because of the high adjustment pressure at the interrelated loads upon the rotary passage, which is then subjected to an early wear.
In order to avoid these difficulties it has been proposed to arrange an additional converter for generating a high adjustment pressure in the radial adjustment head and to connect the additional converter through the rotary transmission with the first converter converting the pneumatic control pressure into liquid pressure, the connection assuring unhindered fluid flow. This results in the rotary transmission being stressed less and in the avoidance of unbalanced conditions caused by losses of leakage oil, compare DE-OS ....(Patent application P 37 26 276.9).
It is further known in installations of the type being discussed here to perform an initial operation prior to each machining process, during which the pressure oil system is filled anew with oil; compare DE-OS 24 26 409 (U.S. Pat. No. 3,977,194).